Zinc dialkyldithiophosphate (ZDDP) is added to engine lubricants to reduce wear and ensure reliable operation. ZDDP reacts under rubbing conditions to form protective zinc/iron phosphate tribofilms on steel surfaces. Recently, it has been demonstrated that this process can be promoted by applied stresses in lubricated contacts, as well as temperature, and is thus mechanochemical in origin. In this study, a tribology test rig capable of applying very high loads has been developed to generate ZDDP tribofilms under full-film elastohydrodynamic lubrication (EHL) conditions in steel/steel ball-on-disk contacts. This provides a well-defined temperature and stress environment with negligible direct asperity contact in which to study mechanochemical processes. ZDDPs with branched primary and secondary alkyl substituents have been studied in three base oils, two with high EHL friction and one with low EHL friction. In the high EHL friction base oils, the tribofilm growth rate increases exponentially with shear stress and temperature for both ZDDPs, as predicted by a stress augmented thermal activation model. Conversely, under otherwise identical conditions, negligible ZDDP tribofilm formation takes place in the low EHL friction base oil. This confirms that the ZDDP reaction is driven by macroscopic shear stress rather than hydrostatic pressure. The secondary ZDDP forms tribofilms considerably faster than the primary ZDDP under equivalent conditions, suggesting that the initial decomposition reaction is the rate determining step for tribofilm formation. The rate of tribofilm growth is independent of ZDDP concentration over the range studied, indicating that this process follows zero-order kinetics. Under full-film EHL conditions, ZDDP tribofilm formation is promoted by macroscopic shear stress applied through the base oil molecules, which induces asymmetric stress on adsorbed ZDDP molecules to promote their decomposition and initiate rapid phosphate polymerisation.

␥-Tocopherol (␥T), the predominant form of vitamin E in diets, but not ␣-tocopherol, the major vitamin E form in tissues and supplements, inhibits proliferation of prostate cancer cells (LNCaP and PC-3) and lung cancer cells (A549). In contrast, at similar concentrations, ␥T has no effect on normal prostate epithelial cells. Combinations of some vitamin E forms, such as ␥T and ␦-tocopherol, exhibit additive or synergistic inhibitory effects. In this study, ␥T or its combination with ␦-tocopherol induced apoptosis in androgen-sensitive prostate LNCaP, but not in androgenresistant PC-3 cells, by the induction of cytochrome c release, activation of caspase 9 and caspase 3, cleavage of poly-ADP-ribose polymerase (PARP), and involvement of caspase-independent pathways. Myriocin and fumonisin B1, specific inhibitors of key enzymes (serine palmitoyltransferase and dihydroceramide synthase, respectively) in de novo synthesis of sphingolipids, significantly protected cells from ␥T-induced DNA fragmentation, cytochrome c release, PARP cleavage, and the formation of active caspase 3. Compared with vehicle-treated controls, ␥T treatment led to pronounced dihydroceramide and dihydrosphingosine accumulation, which preceded morphological and biochemical manifestations of apoptosis. In contrast, ceramide and shpingosine levels did not increase until day 3, when substantial cell death took place. Our study demonstrates that ␥T and mixed vitamin E forms induce cell death by interrupting the de novo sphingolipid pathway in a prostate cancer cell line. Thus, certain vitamin E forms may be valuable as anticancer agents.

Carotenoids are a class of fat-soluble antioxidant vitamin compounds present in maize ( Zea mays L.) that may provide health benefits to animals or humans. Four carotenoid compounds are predominant in maize grain: beta-carotene, beta-cryptoxanthin, zeaxanthin, and lutein. Although beta-carotene has the highest pro-vitamin A activity, it is present in a relatively low concentration in maize kernels. We set out to identify quantitative trait loci (QTL) affecting carotenoid accumulation in maize kernels. Two sets of segregating families were evaluated-a set of F2:3 lines derived from a cross of W64a x A632, and their testcross progeny with AE335. Molecular markers were evaluated on the F2:3 lines and a genetic linkage map created. High-performance liquid chromatography was performed to measure beta-carotene, beta-cryptoxanthin, zeaxanthin, and lutein on both sets of materials. Composite interval mapping identified chromosome regions with QTL for one or more individual carotenoids in the per se and testcross progenies. Notably QTL in the per se population map to regions with candidate genes, yellow 1 and viviparous 9, which may be responsible for quantitative variation in carotenoids. The yellow 1 gene maps to chromosome six and is associated with phytoene synthase, the enzyme catalyzing the first dedicated step in the carotenoid biosynthetic pathway. The viviparous 9 gene maps to chromosome seven and is associated with zeta-carotene desaturase, an enzyme catalyzing an early step in the carotenoid biosynthetic pathway. If the QTL identified in this study are confirmed, particularly those associated with candidates genes, they could be used in an efficient marker-assisted selection program to facilitate increasing levels of carotenoids in maize grain.

disadvantages; alfalfa meal is high in fiber and low in energy; marigold petals are costly and lack nutrients so Carotenoids (provitamin A) and tocopherols (vitamin E) are lipid their use has decreased and replaced by synthetic yellow soluble antioxidants associated with decreased risk of several degenerative diseases. Both vitamins occur naturally in corn (Zea mays L.) pigments. These considerations emphasize a need for grain. Corn grain is a major component in diets of humans and ani-increased levels of carotenoids in corn grain. mals, and may have added value with increased levels of carotenoids The presence of antioxidants in lipids improves their and tocopherols. To estimate genetic variation among a group of stability and delays oil rancidity (Chow and Draper, inbreds and their breeding potential, we estimated combining abilities 1974; Weber, 1987a). Schaefer et al. (1995) and Williams of four carotenoids and two tocopherols in a diallel of 45 corn hybrids. (1997) found vitamin E supplementation in feed delayed Ten inbreds were chosen that varied in endosperm color (yellow to discoloration and prolonged shelf life of packaged beef, orange), tocopherol levels and oil content. Plants were grown for poultry, and food products. Animals fed corn containing two years (1998, 1999) at Urbana, IL, in an RCB design with three high levels of tocopherols could increase profits by rereplications. High pressure liquid chromatography was used to assay ducing waste caused by discolored products. The presfor four carotenoids (lutein, zeaxanthin, ␤-cryptoxanthin, and ␤-carotene) and two tocopherols (␣-tocopherol and ␥-tocopherol). Good ence of natural antioxidants, especially tocopherols, agreement between year means for the six compounds was observed gives corn oil flavor stability during storage and cooking. indicating minor environmental effects. Diallel analyses indicated, Increased levels of tocopherols should enhance shelf between 72 to 87% of the total sums of squares for hybrids for the life of corn oil (Weber, 1987b;Watson, 1988; White and six compounds was attributable to GCA effects. Significant SCA ef-Pollak, 1995). fects were found for several crosses. Estimates of GCA effects indi-Several studies have shown significant differences cated A619 had high values for lutein, ␤-cryptoxanthin, and total among corn inbreds for carotenoid and tocopherol levcarotenoids. Inbred R84 was a poor genotype for xanthophyll pigels. Blessin et al. (1963) reported ranges of 0.9 to 4.1 ments but a significant contributor for ␤-carotene and ␥-tocopherol, g g Ϫ1 for carotenes and 18.6 to 48.0 g g Ϫ1 for xanthoand total tocopherol. These genetic stocks indicate corn hybrids can phylls for 39 corn inbreds. Quackenbush et al. (1963) be developed with higher levels of provitamin A and vitamin E. evaluated 125 inbreds and found provitamin A amounts ranged from a trace to 7.3 g g Ϫ1 , lutein from 2 to 33 g g Ϫ1 . Forgey (1974) evaluated 20 inbreds and found

Illinois long‐term selection strains of maize (Zea mays L.) have been useful for identifying genomic regions controlling kernel oil, protein, and starch concentrations. To identify kernel trait quantitative trait loci (QTL) in a genetic background more relevant to practical breeding, 150 BC1‐derived S1 lines (BC1S1s) were produced from Illinois High Oil and recurrent parent B73. Oil, protein, and starch were measured in BC1S1s and in Mo17‐topcross hybrids (TCs). Kernel mass of BC1S1s and grain yield of TCs were also determined. Starch was positively correlated with mass in BC1S1s (rp = 0.67**, α ≤ 0.01) and with yield in TCs (rp = 0.59**). Oil was negatively correlated with mass in BC1S1s (rp = −0.29**) and with yield in TCs (rp = −0.30**). Oil was negatively correlated with starch in BC1S1s (rp = −0.75**) and TCs (rp = −0.66**). A genetic map with length = 1486 cM was created with 110 markers. Multiple regression models with QTL detected by composite interval mapping (CIM) explained 46.9, 45.2, 44.3, and 17.7% of phenotypic variance for oil, protein, starch, and mass, respectively, in BC1S1s and 17.5, 22.9, 40.1, and 28.7% for oil, protein, starch, and yield, respectively, in TCs. A 22 cM‐interval on chromosome 6 in BC1S1s included oil, protein, and starch QTL, including a QTL explaining 36.7% of the BC1S1 phenotypic variation for oil. No yield QTL were detected in this region. Introgression of this QTL into breeding lines might increase oil while maintaining yield.

Organic friction modifier additives (OFMs) are surfactant molecules added to engine oils to reduce friction in the boundary lubrication regime. They are thought to work by forming an absorbed layer which provides low friction. This paper studied the relationship between the adsorption of OFMs and their friction and wear reducing properties in a rubbing contact formed by a stationary glass ball and a rotating silicon disk under the boundary lubrication regime. The effect of molecular structure was investigated by using OFMs of various tail saturation and head group chemistry. OFM tested were oleic acid, octadecylamine, oleylamine and glycerol monooleate. The thickness of an OFM adsorbed layer in hexadecane, examined in-situ by spectroscopic ellipsometry and quartz crystal microbalance (QCM), depends on the molecular structure and the concentration of the OFM. As expected, saturated, linear chain gives the thickest film. A critical OFM layer thickness of about 0.6 nm is necessary to achieve low initial and maximum friction. The thicker OFM layers are accompanied by narrower wear tracks, which are rougher than the wider, smoother wear tracks formed with thinner OFM layers. The interplay between the thickness of the OFM layer and wear track surface roughness results in all OFM layers having similar steady friction. This shows that the apparent effect of OFM depends on the stage of rubbing test: initially on friction; and then subsequently on surface damage. 2 Despite OFMs and the base oil having similar refractive indices, ellipsometry was found to be a suitable technique for examining the adsorption of OFM additives from an oil based solution, and showed reasonable correlation with QCM results. friction coefficients at the 100 th rotation. This shows that the impact of the properties of OFM adsorbed layers extend beyond the initial friction to the subsequent surface damage.

The molecular weight (M) dependence of the surface diffusion coefficient (D) is measured for polystyrene adsorbed from chloroform, a good solvent, in the dilute limit of surface coverage. On as-received smooth quartz surfaces, we reproduce D ~ M -3/2 , the same power law observed earlier in aqueous systems for a much smaller range of M. This is consistent with computer simulations in the literature regarding 2D diffusion between obstacles. But on smoother surfaces, mica and thermally annealed quartz, we observe Rouse scaling, D ~ M -1 , to our knowledge the first time this theoretically-expected scaling has been observed for polymer diffusion at the solid-liquid interface. For polystyrene of the highest molecular weight diffusing on the rougher surfaces, in the range 1 to 6.7 x 10 5 g-mol -1 , the dependence on M softens to weaker than a power law of -3/2, suggesting reversion to Rouse behavior.

7594 8991This work presents for the first time through-thickness velocity profiles obtained in an EHL contact by photobleached imaging. The velocity profile was inferred by following the evolution of the shape of a photobleached plug formed through the thickness of the fluorescently-doped lubricant, oligomer polybutene (PB), in the contact when shear was applied. The proposed methodology was validated by successfully obtaining the expected linear profile with PB experiencing Couette flow. The methodology was then applied to PB in an EHL contact. The variation of the profiles within the contact area was also investigated.The velocity profile of PB in an EHL contact severely deviates from the common linear assumption and exhibits inhomogeneous shear: three regions of varying shear rate have been observed. The phenomenon is shown to be neither due to thermal nor diffusion effects. PB also shows significant slip at the glass-liquid interface. The amount of slip varies with position in the contact. Possible causes, such as pressure induced viscosity enhancement, as well as the significance of the findings and the benefits of the technique are discussed.The linear velocity profile in an EHL contact is usually assumed for both the film thickness and friction predictions. The profile has however never been measured experimentally until now. This work enables the validation of conventional assumptions and the study of flow heterogeneity of lubricants in a contact. This facilitates an improved understanding of the rheology of confined lubricant and hence more accurate predictions of tribological properties.